The polyimide resin has characteristics such as superior heat resistance, mechanical strength and insulative properties or a low dielectric constant. Therefore, the polyimide resin is used widely as an insulating material or a protective material in electric or electronic parts including various elements or electronic substrates such as a multilayered wiring board. Also, in order to insulate or protect a minute point selectively in precision electric or electronic parts, an insulating film or an overcoating film is preferably formed by photolithography using a photosensitive resin composition from a standpoint of ease of processing.
Conventionally, in photosensitive resin compositions which are applicable to photolithography, a resin having in a side chain a functional group which can react with a base (e.g., a carboxyl group and a phenolic hydroxyl group) or a resin having a reactive group which reacts with an acid or a base to produce a carboxyl group or a phenolic hydroxyl group (a carboxyl group or a phenolic hydroxyl group protected by a protecting group which can be deprotected by acid or a base) can be employed (patent document 1).
However, a polyimide resin usually does not have a reactive group to produce a carboxyl group or a phenolic hydroxyl group by reacting with an acid or a base. Depending on the composition of monomers, a polyimide resin may have such a carboxyl group in a side chain, but the content of the carboxyl group of such a polyimide resin is insufficient to be used as a resin for a photosensitive resin composition.
It is also possible to introduce into a polyimide resin such a reactive group which generates a carboxyl group or a phenolic hydroxyl group by reacting with an acid or a base. However, in this case, there is a problem that the remarkably high cost is required for the synthesis of such a polyimide resin. Thus, it is difficult to blend a general polyimide resin in a photosensitive resin composition for photolithography. Therefore, it is desired to provide a resin composition containing a polyimide resin with photosensitivity by which pattern formation is possible.
A photosensitive resin composition containing a polyimide resin (polyetherimide) and a photo acid generator is proposed to solve such a problem (patent document 2). Upon exposure, the photosensitive resin composition described in patent document 2 is solubilized in a developing solution containing hydroxylamine, N-methyl-2-pyrrolidone and ion exchanged water.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2001-066781
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2003-076013